I made this page to keep track of my firefox extensions, until an export exentions solution came along. This seems to be the case with FEBE and CLEO – two extensions that will let you export/backup your extensions (FEBE) and even package your extensions in .xpi files for easy sharing with others (CLEO).
To answer your question: Yes. It seems to work! I now have 30 backed up extensions in .xpi files on my harddrive – and I have packaged 12 of my favourite plugins for you to try out: 12 Firefox Extensions (1,8 MB .xpi-file)

Still, I have grown a certain fondness of (my still incomplete) list of favourite plugins. So here they are:
Browsing annoyances
IE view – opens page in IE.
View in Firefox – the other way round.
IE Tab – opens tab as IE.
Tabbrowser preferences – enhances tabbed browsing.

Web
Web Developer Toolbar – for the technical approach to browsing.
MeasureIt – pull-out ruler.
ColorZilla – Eyedropper/ColorPicker.
Copy Plain Text – strips formatting from web text.
Copy Links – copies all links on the page to the clipboard.

Blogging
Performancing – well integrated blog plugin for your favourite browser.
Copy as HTML Link – need explanation?
Dictionaries – Add at need.

Ohh – took a screendump of the most important extensions I use at work. I’ll update the list above soonish…
Below the screendump you’ll find a complete list of all the extensions – generated by Firefox extension dumper

• Adsense Notifier 0.9.5
  
  Displays your adsense earnings on the statusbar.
• Charles Autoconfiguration 3.1.1
  
  Autoconfigures Mozilla Firefox for use with Charles Web Debugging Proxy.
• ClickMap 2.3.2
  
  View key site metrics in an intuitive visual format.
• ColorZilla 1.0
  
  Advanced Eyedropper, ColorPicker, Page Zoomer and other colorful goodies
• Copy as HTML Link 1.1
  
  Creates an HTML link to the current page using the selected text and copies it
• Copy Links 0.1.4
  
  Copy multiple URLs in anchors to clipboard.
• Dansk ordbog – Danish Dictionary 1.4.66
• del.icio.us Bookmarks 1.5.44
  
  Access your bookmarks wherever you go and keep them organized no matter how many you have.
• Dictionary Switcher 0.8
  
  Toggles dictionaries automatically or manually and displays the currently selected dictionary in the status bar.
• Digg This! 0.5
  
  adds Digg This! to the right-click or Tools menu.
• DOM Inspector 1.8.1.12
  
  Inspects the structure and properties of a window and its contents.
• Email This! Bookmarklet Extension 2.1.3
  
  Email This! will send a recipient the link, title, and text of the webpage you are viewing.
• Esperanta Vortaro 1.0.1
• Extension List Dumper 1.11.0
  
  Dumps a list of the installed extensions.
• Firebug 1.05
  
  Web Development Evolved
• FireFTP 0.97.1
  
  FTP Client for Mozilla Firefox.
• FireShot 0.32
  
  Adds the ability to take a screenshot of the page, edit it and save, copy to clipboard, send to external editor or e-mail it.
• Foxmarks Bookmark Synchronizer 2.0.43
  
  Synchronizes your bookmarks across machines.
• Furl Tools 0.8
  
  Gives menu and button options for accessing Furl.
• Google Calendar Quick Add 1.6.3
  
  A shortcut to add calendar entries quickly without having to open Google Calendar.
• Greasemonkey 0.7.20080121.0
  
  A User Script Manager for Firefox
• Html Validator 0.8.4.0
  
  Adds HTML validation to the View Page Source of the browser. The validation is done by Tidy from W3c.
• IE View Lite 1.3.1
  
  Cut down version of IE View by Paul Roub.
• Java Console 6.0.03
• Java Console 6.0.02
• LinkedIn Companion for Firefox 3.0.1
  
  Accelerate your business and career through LinkedIn
• MeasureIt 0.3.6
  
  Draw out a ruler to get the pixel width and height of any elements on a webpage.
• Organize Status Bar 0.5.2
  
  Organise your status bar icons.
• PicLens 1.6.1.1029
  
  Discover More
• ScribeFire 1.4.2
  
  A full-featured blog editor that integrates with your browser and lets you easily post to your blog.
• SearchStatus 1.21
  
  Display the Google PageRank and Alexa ranking with search-related tools.
• ShowIP 0.8.05
  
  Show the IP address of the current page in the status bar. It also allows querying custom services by IP (right mouse button) and Hostname (left mouse button), like whois, netcraft. Additionally you can copy the IP address to the clipboard. This extension was formerly known as ipv6ident.
• Sphinn Button 1.0
  
  A toolbar button that lets you to Sphin the active tab
• Svensk ordlista 1.4
• Tab Mix Plus 0.3.6
  
  Tab browsing with an added boost.
• Talkback 2.0.0.12
  
  Sends information about program crashes to Mozilla.
• United States English Dictionary 2.0.0.6
  
  English United States (en-US) spellchecking dictionary
• Uploadr for Flickr 1.0
  
  Upload images to flickr
• User Agent Switcher 0.6.10
  
  Adds a menu and a toolbar button to switch the user agent of the browser.
• Web Developer 1.1.4
  
  Adds a menu and a toolbar with various web developer tools.
• Word Count 0.4
  
  Counts the number of words in selected text.
• YSlow 0.9.2
  
  Make your pages faster with Yahoo!’s performance lint tool.